However, CIO UK sister title Computerworld UK has confirmed with the bank that some Ulster Bank customers in Ireland are still being affected by the botched upgrade that was made to batch processing software CA 7 from CA Technologies.

RBS has said that it will refund customers who face fees and charges as a result of the IT failure, as well as covering ‘out of pocket expenses’ and ensuring that customer credit ratings aren’t negatively affected.

"All of our systems are running as normal this morning in the timeframes we would expect and normal service has now been restored for the majority of our customers. Given the scale of the incident, the clean-up continues and a small percentage of outstanding transactions are being processed over the next couple of days,” said an RBS spokeswoman.

She added: “There is no doubt that there will be reconciliations to some customer accounts that also need to take place over the coming days and weeks. However, for the majority of customers it is now business as usual.”

“As normal service resumes for our customers, we are beginning the job of ensuring that customers who have been adversely impacted by this issue are put back to where they would have been had this problem not occurred.”

This contradicts earlier media reports that claimed a junior IT worker based in India had made the error.

In his letter to Andrew Tyrie, chairman of the committee, CEO Stephen Hester wrote: “The initial reviews we have carried out indicate that the problem was created when maintenance on systems, which are managed and operated by our team in Edinburgh, caused an error in our batch scheduler.

“This error caused the automated batch processing to fail on the night of Tuesday 19 June. The knock-on effects were substantial and required significant manual interventions from our team, compounded because the team could not access the record of transactions that had been processed up to the point of failure.

“The need to first establish at what point processing had stopped delayed subsequent batches and created a substantial backlog.”